Are Clouds?] [Types
of Clouds] [Online Activity]
need accurate weather reports to make air travel safe
for their passengers. Certain types of weather conditions can
put a plane and its passengers in danger. Very high winds and
severe thunderstorms are some examples of weather conditions
that make air travel unsafe. Sometimes a plane does not takeoff
at its scheduled time because
conditions. This weather delay happens
because it is very important to pilots and airlines that their
passengers are kept safe!
Airlines and pilots rely on weather forecasters (called meteorologists) to
tell them what kind of weather to expect. They talk to these aviation weather
forecasters and flight dispatchers to find out about weather conditions
en route and at their destination. They use the information to choose a
route, altitude, and speed for a safe, smooth flight. But they can also
look to the sky for clues from nature's road map! Clouds can send us messages
about the weather if we know how to read them.
WHAT ARE CLOUDS?
Heat from the sun causes water on earth from rivers, lakes
or oceans to go into the air and change into a gas called
water vapor. This is called evaporation.
Clouds are formed from warm air that rises from the earth carrying water vapor
in it. The water vapor cools as the warm air rises higher. When it cools
it changes into droplets of water (or crystals of ice.) Clouds form when
these droplets of water collect around small bits of dust, sea salt or
pollution floating in the air. The word for this is condensation.
The droplets bump into each other and get bigger and bigger. When the water
droplets become too heavy to stay in the air they fall to the ground as
rain or snow. Another word for rain or snow is precipitation. Some of this
precipitation will collect into the rivers, lakes and oceans on earth and
start the cycle all over again!
TYPES OF CLOUDS
Some clouds are so low they touch the ground, while others
are high in the sky. Clouds come in many shapes. Pilots
can predict the weather just by
watching the clouds and the direction they are moving in. Clouds can give
them messages about what the weather will be like many hours in advance.
Just by studying a cloud's shape they can tell a great deal about the cloud.
There are three basic kinds of clouds.
Cirrus clouds are thin with fuzzy edges that look like feathers. They are high
in the sky. They are so high that they are made up of ice particles. The
winds that are high in the sky are often different from the winds direction
on the ground. If the cirrus clouds are moving from right to left (high
pressure) the weather will be warmer. If the cirrus clouds are moving from
left to right (low pressure) on a summer day colder weather with rain may
clouds look like puffs of cotton with flat bottoms piled in a
heap. They are usually nearer the earth than cirrus clouds. Cumulus
clouds puffy and white mean fair weather will continue. Cumulus
clouds that stack up, turn dark gray and grow taller early in
the day can turn into thunderstorms later.
word NIMBUS added to a clouds name means that rain or snow is
falling from the cloud.
clouds are the thunder clouds that bring strong winds, hail and
rain on a summer day. They are a type of cumulus cloud.
clouds are low, flat sheets of clouds that are the lowest clouds
in the sky. They are often dark and can bring long lasting rain
or snow flurries. When stratus clouds are close to the ground
they are called fog. These clouds can create poor visibility
for pilots. Stratus clouds can stay in one place for several
days. These clouds can stretch for hundreds of miles!
that you have learned more about clouds and the messages
they send us,
try the Cloud Clues Activity to
test what you know!
HINT: You might want to write down the names of the three types
clouds before you take the test.
will need Macromedia's free Flash Player 6 to view
and use this activity.
If the activity does not work in your browser, please click on the icon
follow the instructions to download and install the Player.